Aquarium filter



FIG. 1 is a perspective view of the filter;

FIG. 2 is a top plan view of the filter;

FIG. 3 is a right side elevational view of the filter;

FIG. 4 is a front elevational view of the filter;

FIG. 5 is a rear elevational view of the filter;

FIG. 6 is a left side elevational view of the filter; and,

FIG. 7 is a bottom plan view of the filter.

The broken line showing is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for an aquarium filter, as shown and described. 